Chapter 14

Question 1

DNA is made of:

Answer 1

• a 5-carbon sugar called deoxyribose
• a phosphate group (PO4)
• a nitrogenous base
• adenine, thymine, cytosine, guanine

Question 2

nucleotides are made of:

Answer 2

• a nitrogenous base at the 1’ carbon
• a phosphate group (-PO4) at the 5’ carbon
• a hydroxyl group (-OH) at the 3’ carbon

Question 3

the phosphate group and hydroxyl group are bond with …

Answer 3

phosphodiester bond

Question 4

Chargaff’s Rule

Answer 4

• amount of A = amount of T
• amount of C = amount of G

Question 5

Double helix:

Answer 5

• 2 sugar-phosphate “backbones”
• N-bases toward the interior form H-bonds with complementary bases on the opposite strand
• strands are anti- parallel

Question 6

DNA replication was semiconservative

Answer 6

After 1 replication, DNA consisted of a 14N-15N hybrid only
After 2 replications, DNA consisted of 2 types of molecules:
-half a 14N-15N hybrid
-half only 14N

Question 7

Both strands of DNA act as … for the …

Answer 7

templates, synthesis of new strands

Question 8

DNA replication requires:

Answer 8

Parental DNA, DNA polymerase enzymes, and nucleotides

Question 9

DNA replication includes:

Answer 9

• initiation: at an origin
• elongation: synthesis of new strands of DNA by DNA polymerase
• termination: terminated differently in prokaryotes (circular chromosomes) and eukaryotes (linear chromosomes)

Question 10

Prokaryotic chromosomes are …

Answer 10

circular DNA molecules

Question 11

In prokaryotes DNA replication occurs during …

Answer 11

binary fission

Question 12

In prokaryotes DNA … bind to … and replication proceeds in … around the chromosome

Answer 12

polymerases, origin, both directions

Question 13

In prokaryotes Key enzymes involved:

Answer 13

• helicase
• DNA gyrase
• primase
• DNA polymerase III (pol III)
• all move from 5’ to 3’

Question 14

helicase

Answer 14

unzips double helix

Question 15

DNA gyrase

Answer 15

unwinds the helix and keeps it from kinking up

Question 16

primase

Answer 16

adds a short RNA primer sequence to the DNA

Question 17

DNA polymerase III (pol III)

Answer 17

adds nucleotides one at a time to the 3’ end of the new (daughter) strand of DNA

Question 18

DNA replication is …

Answer 18

semidiscontinuous

Question 19

leading strand

Answer 19

synthesized continuously (in the same direction that replication enzymes are moving), 5’ to 3’

Question 20

lagging strand

Answer 20

is synthesized discontinuously, 3’ to 5’

Question 21

DNA polymerases

Answer 21

• Matches DNA bases with complementary nucleotides and adds them
• All have several common features
  *Add new nucleotides to 3′ end of new strands (synthesize in 5′-to-3′ direction)
  *Require an RNA primer to start

Question 22

The enzymes for DNA replication are contained within the …

Answer 22

replisome

Question 23

The replisome consists of

Answer 23

• the primosome: composed of RNA primase and helicase
• 2 copies of DNA polymerase III (pol III)

Question 24

E. coli has 3 DNA polymerases:

Answer 24

• DNA polymerase III (pol III): Main replication enzyme
• DNA polymerase I (pol I): Removes RNA primers from lagging strand and replaces them with DNA
• DNA polymerase II (pol II): Used for DNA repair

Question 25

DNA replication occurs during

Answer 25

S phase of interphase

Question 26

The larger size and complex packaging of eukaryotic chromosomes means they must be replicated from ...

Answer 26

multiple origins

Question 27

Initiation requires more factors to assemble both ... and ... onto the DNA strand, then load ...

Answer 27

helicase, primase, DNA polymerase

Question 28

Primase includes both a ...

Answer 28

DNA and RNA polymerase

Question 29

Main replication polymerase is a complex of ...

Answer 29

DNA polymerase epsilon (pol ε) and DNA polymerase delta (pol δ) (similar function as pol III in prokaryotes).

Question 30

Synthesizing the ends of the chromosomes is difficult ...

Answer 30

because of the lack of a primer (primase cannot put RNA there).

Question 31

With each round of DNA replication, the linear eukaryotic chromosome ...

Answer 31

could become shorter

Question 32

telomeres

Answer 32

repeated DNA base sequences at each ends of eukaryotic chromosomes

Question 33

telomeres are repairs by ...

Answer 33

telomerase enzyme

Question 34

telomerase contains ...

Answer 34

an RNA region that is used as a template so a DNA primer can be produced

Question 35

as long as telomerase is working well, ...

Answer 35

the chromosomes do not shorten much

Question 36

mutations

Answer 36

Mistakes during DNA replication can happen

Question 37

DNA can also be altered by chemical or physical agents called

Answer 37

mutagens

Question 38

specific DNA repair:

Answer 38

- targets a particular type of mutation - Example: repair of thymine dimers by photolyase

Question 39

mismatch

Answer 39

incorrect base pair

Question 40

Mismatch repair enzymes

Answer 40

detect and remove the base from the newly synthesized strand. Gap is filled with the correct base by DNA pol II

Question 41

Non-specific DNA repair

Answer 41

- can repair many different kinds of damage - Example: excision repair corrects damaged or mismatched bases

Question 42

point mutations

Answer 42

- base substitutions - Ex. silent, missense, nonsense

Question 43

silent mutation

Answer 43

has no effect on the protein sequence

Question 44

missense mutation

Answer 44

results in an amino acid substitution

Question 45

nonsense mutation

Answer 45

substitutes a stop codon for an amino acid

Question 46

frameshift mutations

Answer 46

insertions or deletions of nucleotides may result in a shift in the reading frame on insertion of stop codon

Question 47

chromosomal mutations

Answer 47

- change in chromosome structure - Ex. deletion, duplication, inversion, translocation

Question 48

deletion mutation

Answer 48

part of chromosome is lost

Question 49

duplication mutation

Answer 49

part of chromosome is copied

Question 50

inversion mutation

Answer 50

part of chromosome is reversed

Question 51

translocation mutation

Answer 51

part of chromosome is moved